Magnetohydrodynamic installation with high temperature heat exchanger



Feb.23, 1965 G. BAUMANN MAGNETOHYDRODYNAMIC INSTALLATION WITH HIGH TEMPERATURE HEAT EXCHANGER 2 Sheets-Sheet 1 Filed July 16, 1962 Gusfi m; Baumann JBE JWX. m ATTORNEYS Feb. 23, 1965 s. BAUMANN 3,170,510

MAGNETOHYDRODYNAMIC INSTALLATION WITH HIGH TEMPERATURE HEAT EXCHANGER Filed July 16, 1962 2 Sheets-Sheet 2 INVENTOR G-u scur Baumamn /fim JWAMMMW ATTORNEY .S

United States Patent 3,170,510 MAGNETOHYDRODYNAMIC INSTALLATION WITH HIGH TEMPERATURE HEAT EX- CHANGER Gustav Baumann, Gehenstorf, Aargau, Switzerland, assignor to Aktiengesellschaft Brown, Boveri & (lie, Baden, Switzerland, a joint-stock company Filed July 16, 1962, Ser. No. 210,094 Claims priority, application Switzerland, July 17, 1961, 8,400/61 6 Claims. (Cl. 165-104) The present invention relates to a'magnetohydrodynamic installation with preheating of the combustion air by means of the exhaust gas of the magnetohydrodynamic generator.

The gas flowing through a magnetohydrodynam'ic generator must be brought to a high temperature in order to attan the necessary electrical conductivity of the gas for the energy generation. These high temperatures can only be obtained by an extensive pre-heating of the combustion air or by enriching the latter with oxygen. The first mentioned possibility requires a specially constructed heat exchanger which can work in the region of 2500 K. The second way impairs the overall efficiency by about 2% and involves an increase in total capital costs of about 5%.

Up till now only heat exchangers of a conventional construction were proposed for the magnetohydrodynamic generator for example tube type heat exchangers. Under the given conditions of high temperature and large pressure diiferences between the hot exhaust gases and the combustion air, there arise very great difiiculties in the construction and the operation of the heat exchanger. From the most recent publications it arises that at the moment there is no technically possible conception in view and thus only such installations are considered to have promise of success as require, due to oxygen-enrichment of the combustion air, no high-temperature heat exchanger. With this method one must bear in mind the substantial economical disadvantages.

The heat exchanger principles being considered have for the aforementioned application the following disadvantages: with tube type heat exchangers, the avail able materials have a great sensitiveness to temperature changes. Because of the strong temperature surge occurring with operational disturbances such a heat exchanger can be completely destroyed. In addition, considerable fabrication difiiculties arise with the working of the suggested construction materials for which especially zirconium oxide comes into question. With regenerators according to the Ljungstrom principle with the basket construction, the strong temperature changes must be considered; furthermore considerable sealing problems arise, these leading to costly solutions and because of the leakage bringing a deterioration of the efficiency. Regenerators with reposing storage mass and reversal control of the gas flows are not practical for the appointed task because the jacketing would be subjected to very strong temperature change. Furthermore from the technical and economic viewpoints, reverse control components for ducts of 2.5 4 metres diameter cannot be designed due to the temperature variations and the consequent leakages. According to a known design, the heat exchanger has a shaft-form with which arrangement a subpartition separates the hot from the cold medium and small solid bodies, which fall down, serve for heat-storage and -transfer. This arrangement is, however, provided and suited for temperatures of up to 1500" C. only and for more or less equal working pressures of the hot and cold media. There are also recognized types of heat-exchangers in which the small heat-storing bodies,

3,170,510 I Patented F eb. 23, 1965 whose direction of flow is repeatedly reversed by builtin bafiie plates, fall down and thus operate as a heattransfer medium between the two gaseous media. The uncooled built-in components limit, however the application of such a heat exchanger to relatively low temperatures or necessitate a comparatively complicated design and thus greater expense, in as much as the builtin components must be cooled. in addition there arise additional heat losses. It is also a recognized procedure to create compartments of greater residence-times in heat exchangers having a finely granulated storage mass which does not move in free fall; this enables the operation to be brought equally to an end. At the same time these compartments operate as separators between the two gaseous media taking part in the heat exchange.

Due to the disadvantages quoted and the incompleteness of the known heat exchangers operating with a finely granulated moving heat-storage mass, a revised, more efficient heat exchanger type must be sought for application to magnetohydrodynamic installations.

In accordance with the invention, a solution was found with which the elements performing the heat exchange can endure very high temperatures and strong temperature change, and the jacketing held to an approximately constant temperature. In such a high temperature heat exchanger for gaseous media, granular, heat-storing bodies traverse in free fall and in a manner recognized in itself, at least two chambers having a gaseous medium flowing through them, as to which the bodies accept heat in the one chamber from the hotter gaseous medium i.e. the discharge gas from the generator and give the heat up in the second chamber to the colder gaseous medium, i.e. the combustion air from the air compressor.

A constructional example of the invention is schematically represented in the drawings. FIG. 1 shows the general arrangement of a magnetohydrodynamic installatiom.

FIG. 2 shows the complete arrangement of a high temperature heat exchanger; FIGS. 3 and 4 show variations of this heat exchanger and FIGS. 5 and 6 show suitable constructions of ball flow control valves for the heat exchanger.

As can be seen in FIG. 1, the compressor 31 forces the combustion air through the high temperature heat exchanger 32 into the magnetohydrodynamic generator 33. The exhaust gases from the latter flow firstly through the heat-exchanger 32, at which point they give up a portion of their heat-content to the combustion air which is to be heated up, and are further utilized in the adjacent boiler 34 of steam circuit 35'. The steam circuit 35 includes in addition the steam turbine 36 fed from boiler 34 and which drives the compressor 31, the useful-power.

steam turbine 37 also fed from boiler 34 and which drives electrical generator .38, the condensers 39 and 40 at the outlet sides of turbines 36, 37 and the boiler feed pumps 41 and 42 for the return of water from the condensers to the boiler 34.

The high temperature heat exchanger 32 as according to the invention working with heat-storing bodies, consists basically of two shaft-like chambers 1 and 2 which are arranged one on top of the other as in FIG. 2, and which are connected with one another through the shut-off component 3, the sluices 4 and the throttling components 5. The granular heat-storing bodies-preferably small balls of heat resistant material e.g. of a ceramic mass, hereinafter referred to simply as balls-come from the distributor 6 into the upper chamber 1 through which they pass in free fall. The function of the distributor is to distribute the balls equally over the cross-section of the chamber in order to gain the best thermal operation. On their passage through the chamber 1 through which hot gas flows, the balls are heated and fall into the intermediate storage space into the related sluice in which case the related throttling component is closed. Each intermediate storage space is dimensioned suificiently large as tobe able toaccept at least a sluice-full of balls. The shut-off component 3 is now closed and the throttling component 5 opened, whereupon the balls-due once i more to theirown weightflow out of the sluice into the distributor 8. After complete emptying of the sluice it is bolted with the throttling component 5 against the chamber 2 and is readyfor the next acceptance of a load of balls out of the intermediate storage space. During this operation the second sluice beginsto fill and the third is already waiting on the emptying. Thus the three sluices come alternately into action and the distributor 8 is regularly charged. The opening and closing of the sluices and the corresponding shut-off and throttling components in the desired time sequence can be automatically controlled from a time-relay.

I The shut-oft component 3 and the throttling component 5 can be of the same construction. As an example of a suitable design, a rotary valve 27 is" shown in FIG. 5. By employing the intermediate storage space it is achieved that during the shutting operation only relatively few balls flow through the throttling component, this making the operation of closing easier. With difiering working pressures in the chambers 1 and 2 the heaping of the balls in the intermediate storage space reduces appreciably the leakagelosses, so that relatively large plays are allowable at the shutolt and throttling components.

From the distributor 8 the hot balls reach the chamber 2 through which they pass in free fall. This distributor has also the task of distributing the balls equally over the cross-section of the chamber in order that the balls give up as much as possible of their stored heat to the cold gas flowing through the chamber 2.

Inmany cases-there will be present in chamber 2 a much higher pressure than in chamber 1, if, for example, the combustion air coming from a compressor flows through the lower chamber and hot exhaust gas through the upper chamber. On emptying sluice 4 there results a pressure equalization with'chamber 2. If throttling component 5 is now closed and the shut-off component 3 opens then the gas trapped 'in the sluice expands and a gas thrust acts on the ball heap in the intermediate storage space, the pile being thus loosened and the pouring out facilitated.

In the lower part of the chamber 2 the balls are gathered in a heap 9. This serves as a seal against the store It a definite pile height must therefore be maintained vertically. With a ball diameter of one millimetre and an inner pressure of 8 atmospheres gauge in the chamber 2 a pile height of about 700 millimetres sufiices to prevent the leakage losses exceeding 1%. e

Thesupervision and control of the level height of a heap can be obtained by hand or automatically. VJitn an arrangement for the automatic control an impulse is I released with the aid of a radiation source 11 and a radiation receiver 12 by blocking or freeing of the radiation path; the said impulse actuates the throttling component 13 in the flowconnection 14. It is of advantage to arrange two radiation sources and two radiation receivers at different heights, their impulses acting on the throttling component 13 in order to be able to control in this way the maximum and minimum heights of the heap.

The throttling component 13 must be so shaped that no 7 balls are crushed by its to and fro'motion and that not too large a controlling force is required. This, may be solved, for example, in the following ways: either by means of a repressing component or a key-shaped displacement element 28 as is represented in FIG. 6..

If both chambers are operated with the same pressure or chamber l with a higher pressure than chamber 2 then the sluices 4 can be omitted Y lar to 9 as described above for chamberZ.

After giving up theirheat the'balls are normally fed anew into the process, .This'can result over section 15 with pneumatic-yet also with mechanical-transport, e.g. with a bucket system. There needbe no anxiety over diiiiculties in the working of the latter as theoperation in questiontakes place at the coldest pointof the installation.

The jaclreting t6 and 170i chambers l aridZ is designed with several wallsand isilushed through with cold gas as a cooling medium in which case the gas enters atl8 into the jacketingltta as in PEG. 2 and at .19 leaves again, while for chamber 2 theheat exchange, process medium to be warmed. is drawn in. it can also be used for the cooling of chamber 1 before it enters chamber 2; at the same time,

however, it must be borne in mind that the colder medium has. often a much higher pressure. than that inthe inner space of chamber 1. Another possibility for wall cooling may beeasily realized with such installations .as have a further. circuit inserted for the'utilization of theexhaust heat, while the working medium of the latter, e.g. water or steam, is conducted through cooling tubes 20 (FIGS. 3 and 4) betweenithe double walls 21 and-22 of the'chambers 1 and 2. A cooling of the sluices is also provided.

The incipient hot gas discharged from generator 33' enters chamber 1 at 23 through the innerspace of which it flows in the opposite direction to that of the falling balls, whereupon it gives up a portion of its heat to the latter and is drawn out of the said chamber at24.

The'cold gas from compressor Sit-which is to be' heated up enters chamber 2 at 25, cools firstly the shell 17 and flows finally in the opposite direction to that of the falling balls-from which it draws off alarge portion of their heat-through the inner space of chamber 2 which'it leaves at 26 as a highly-heated gas. a

If the output required from the heat. exchanger should alter, then it is advantageous to alter too the charging rate of: the balls per unit time. A simple possibility for this is offered with the transport over section 15, during which more or-less balls are taken from the store 10. If a decrease in output of the-heat exchanger shouldextend over a longer period of time then the waiting time for the balls between two transits would be lengthened and there would-be lost too much of the residual heat still stored up in them. One Will thus alter too, in proportion to the charging rate, the total quantity of balls participating in the process; In the same way unavoidable quantity losses caused by abrasion and control operations can be replaced.

Hand in hand with the alteration of the charging rate goes an influence of the ball flow through the throttling component 5; in all cases too a temporary alteration in the rhythm of the sluice which can be'easily caused by a displaced setting of the time relay.

The size of the granular heat-storing bodies, or,- respectively, the diameter of the balls, the gas velocity and the falling height of the balls are all directly related to one another and are decisive for the output of the heat exchanger. The gasvelocity not only determines the heat transfer but also influences the falling speed of the balls, which is extensively dependenta'gain on theball-diameter. Falling height and falling speed, are, however, the param eters for the duration of fall'of the balls which respectively must have enough time to be able to accept the desired heat quantity and again to be able to give itup. By the correct balance between the raising force of'thefiowing gas and the weight-force which are working on the i more than two gases take part in the heat exchange or the same gas is to receive or give up heat during a process more than once in the heat exchanger. In addition the chambers can be arranged beside one another; then, however, the weight of the balls cannot be utilized for transport and there must be arranged between each two chambers a transporting device for the conveyance of the balls.

With working pressures in both chambers of roughly the same magnitude, the sluices between these chambers are not absolutely necessary A contraction similar to a bottle neck or an hour glass would also. suffice. With larger pressure differences between the two chambers the leakage losses would steeply rise and a ball transport caused solely by weight would be impossible.

The heat exchanger according to the invention has the advantage that its own storage mass is very small; it thus follows immediately any load alterations, is not sensitive to rapid temperature change and not endangered by working disturbances. In normal service each component part has an approximately constant temperature. The heat-storing bodies can be produced at little cost and can be replaced quickly and simply without involving at the same time a break in operation.

With the aid of such a high temperature heat exchanger the efiiciency of a magnetohydrodynamic installation is improved and the plant capital costs lowered; it is thus of twofold advantage.

I claim:

1. A heat exchanger for pre-heating high pressure combustion air, said heat exchanger including upper and lower shaft-like chambers arranged one above the other and through which discrete bodies capable of storing and also discharging heat corresponding to their mass and specific heat pass in a free fall manner, a first distributor for said heat storing bodies located at the upper entrance end to said upper chamber, a second distributor for said heat storing bodies located at the upper entrance end to said lower chamber, a plurality of intermediate storage spaces for said bodies located at the lower end of said upper chamber, each said storage space terminating in an outlet, a passageway individual to each said outlet and which serves to connect the same with said second distributor, each said passageway including a sluice chamber for temporarily holding said bodies collected in the storage space correlated thereto as well as a shut-off valve located between the entrance to said sluice chamber and said outlet from said storage space and also a throttle valve located between the exit from said sluice chamber and said second distributor, means for passing lower pressure hot exhaust gas through said upper chamber in heat-exchange relation with said free falling bodies to transfer heat thereto, means for passing higher pressure combustion air through said lower chamber in heat-exchange relation with the heated free falling bodies to transfer heat to the combustion air, and means opening and closing each said shut-off valve and the throttle valve correlated thereto in an alternate manner so that the sluice chamber correlated thereto is filled with said shut-cit valve open and said throttle valve closed and is thereafter emptied with said shu -off valve closed and said throttle valve open, whereby such higher pressure combustion air from said lower chamber as is trapped within said sluice chamber upon emptying thereof by upward flow through said passageway is thereafter discharged upwardly into said storage space correlated thereto upon re-opening of said shut-off valve and re-closing of said throttle valve for loosening said bodies therein prior to the next discharge into said sluice chamber, said lastmentioned means also actuating said shut-off and throttle valves for said passageways in a sequential manner such that said sluice are filled and emptied'in succession.

2. A heat exchanger construction as defined in claim 1 and which further includes a storage space for the bodies located below the discharge end of said lower chamber and connected therewith by a discharge passageway, and a throttling valve in said discharge passageway for so controlling the rate of discharge of the bodies from said lower chamber that a pile of said bodies is maintained Within.

the lower portion of said lower chamber, said pile of the bodies serving as a gas seal to prevent leakage of the higher pressure combustion air through said discharge passageway.

3. A heat exchanger construction as defined in claim 2 and which further includes a source of radiation located to one side of said lower chamber and a radiation receiver located at the opposite side of said lower chamber for supervision and control of the level of said body pile.

4. A heat exchanger construction as defined in claim 1 wherein said lower chamber has a double wall structure and said higher pressure combustion air is passed through the space between the double walls prior to entering said lower chamber.

5. A heat exchanger construction as defined in claim 1 wherein said upper chamber has a double wall structure, and means for passing a cooling gas through the space between the double walls.

6. A heat exchanger construction as defined in claim 5 wherein the space between double walls of said upper chamber is cooled by the higher pressure combustion air prior to entering said lower chamber.

References Qited in the file of this patent UNITED STATES PATENTS 2,118,334 Wilson May 24, 1938 2,631,835 Jones Mar. 17, 1953 2,741,547 Alleman Aug. 10, 1956 2,750,158 Forkel June 12, 1956 2,796,237 Nettel June 18, 1957 2,946,132 Armstrong July 26, 1960 I FOREIGN PATENTS 772,837 Great Britain Apr. 17, 1957 

1. A HEAT EXCHANGE FOR PRE-HEATING HIGH PRESSURE COMBUSTION AIR, SAID HEAT EXCHANGER INCLUDING UPPER AND LOWER SHAFT-LIKE CHAMBERS ARRANGED ONE ABOVE THE OTHER AND THROUGH WHICH DISCRETE BODIES CAPABLE OF STORING AND ALSO DISCHARGING HEAT CORRESPONDING TO THEIR MASS AND SPECIFIC HEAT PASS IN A FREE FALL MANNER, A FIRST DISTRIBUTOR FOR SAID HEAT STORING BODIES LOCATED AT THE UPPER ENTRANCE END TO SAID UPPER CHAMBER, A SECOND DISTRIBUTOR FOR SAID STORING BODIES LOCATED AT THE UPPER ENTRANCE END TO SAID LOWER CHAMBER, A PLURALITY OF INTERMEDIATE STORAGE SPACES FOR SAID BODIES LOCATED AT THE LOWER END OF SAID UPPER CHAMBER, EACH SAID STORAGE SPACE TERMINATING IN AN OUTELT, A PASSAGEWAY INDIVIDUAL TO EACH SAID OUTLET AND WHICH SERVES TO CONNECT THE SAME WITH SAID SECOND DISTRIBUTOR, EACH SAID PASSAGEWAY INCLUDING A SLUICE CHAMBER FOR TEMPORARILY HOLDING SAID BODIES COLLECTED IN THE STORAGE SPACE CORRELATED THERETO AS WELL AS A SHUT-OFF VALVE LOCATED BETWEEN THE ENTRANCE TO SAID SLUICE CHAMBER AND SAID OUTLET FROM SAID STORAGE SPACE AND ALSO A THROTTLE VALVE LOCATED BETWEEN THE EXIT FROM SAID SLUICE CHAMBER AND SAID SECOND DISTRIBUTOR, MEANS FOR PASSING LOWER PRESSURE HOT EXHAUST GAS THROUGH SAID UPPER CHAMBER IN HEAT-EXCHANGE RELATION WITHL SAID FREE FALLING BODIES TO TRANSFER HEAT THERETO, MEANS FOR PASSING HIGHER PRESSURE COMBUSTION AIR THROUGH SAID LOWER CHAMBER IN HEAT-EXCHANGE RELATION WITH THE HEATED FREE FALLING BODIES TO TRANSFER HEAT TO THE COMBUSTION AIR, AND MEANS OPENING AND CLOSING EACH SAID SHUT-OFF VALVE AND THE THROTTTLE VALVE CORRELATED THERETO IN AN ALTERNATE MANNER SO THAT THE SLUICE CHAMBER CORRELATED THERETO IS FILLED WITH SAID SHUT-OFF VALVE OPEN, WHEREBY SUCH HIGHER CLOSED AND IS THEREAFTER EMPTIED WITH SAID SHUT-OFF VALVE CLOSED AND SAID THROTTLE VALVE OPEN, WHEREBY SUCH HIGHER PRESSURE COMBUSTION AIR FROM SAID LOWER CHAMBER AS IS TRAPPED WITHIN SAID SLUICE CHAMBER UPON EMPTYING THEREOF BY UPWARD FLOW THROUGH SAID PASSAGEWAY IS THEREAFTER DISCHANGED UPWARDLY INTO SAID STORAGE SPACE CORRELATED THERETO UPON RE-OPENING OF SAID SHUT-OFF VALVE AND RE-CLOSING OF SAID THROTTLE VALVE FOR LOOSENING SAID BODIES THEREIN PRIOR TO THE NEXT DISCHARGE INTO SAID SLUICE CHAMBER, SAID LASTMENTIONED MEANS ALSO ACTUATING SAID SHUT-OFF AND THROTTLE VALVES FOR SAID PASSAGEWAYS IN A SEQUENTIAL MANNER SUCH THAT SAID SLUICE ARE FILLED AND EMPTIED IN SUCCESSION. 